1. Field of Invention
The present invention relates to a light emitting device, and more particularly to a light emitting device with uniform distribution of light emitting intensity.
2. Description of Related Art
Referring to FIG. 1A, FIG. 1B and FIG. 2, the conventional light emitting device 100 comprises a substrate 110, a plurality of light-emitting diode (LED) chips 120 and a lens array 130. The LED chips 120 are disposed on the substrate 110, and arranged in a 2×2 array. The lens array 130 is disposed on the substrate 110, and wraps the LED chips 120. The lens array 130 comprises a plurality of lenses 132, wherein each lens 132 corresponds to an LED chip 120, and the light exit surface 133 of each lens 132 is a pyramidal recessed surface.
Accordingly, the lens array 130 is used to increase the light emitting amount of the LED chip 120, so as to prevent the light emitted by the LED chips 120 from generating total reflection in the LED chips 120 and then failing to emit out of the LED chips 120. Moreover, the LED chips 120 comprises a red light LED chip 121, a blue light LED chip 122 and two green light LED chips 123. The red light, green light and blue light emitted by the LED chips 120 can be blended to form the white light.
However, for FIG. 1B, a lens 130 wrapping the green light LED chip 123 exists on the left of the red light LED chip 121, and no lens exists on the right of the red light LED chip 121, such that the light-emitting pattern of the light 124 emitted by the red light LED chip 121 is asymmetric. Similarly, in different cross-sections, the problem of the asymmetric light-emitting pattern also exists. It is found in the practical measurement that the phenomenon of asymmetric light-emitting pattern is quite distinct.
FIGS. 3A to 3D are respectively light-emitting pattern views of the red light LED chip measured from the viewing surfaces S1 to S4 in FIG. 1A. Referring to FIGS. 3A to 3D, it is shown from FIGS. 3A to 3C that the light-emitting patterns of the red light LED chip 121 measured from the viewing surfaces S1 to S3 (referring to FIG. 1A) are relatively asymmetric. In other words, the distribution of the light emitting intensity of the red light of the light emitting device 100 is asymmetric. Similarly, the distribution of the light emitting intensity of the blue light and the green light of the light emitting device 100 may also be asymmetric, such that the problem of non-uniform blending of the light may be generated, and the light from the specific angles may be bluish, greenish, or reddish.